This invention consists of a highly efficient beamforming system that captures most of the light from a substantially omnidirectional source, without the need for mirrors and their attendant surface losses. One or more of the lens elements are centrally situated to be either integral with a hot light source or in optical contact with a cold light source. A hot light source, such as an incandescent lamp, is one that operates via thermal emission from a component (i.e., filament) that is at an elevated temperature. Other examples are arc lamps and discharge lamps. A cold light source utilizes some other means than heat to generate light. Examples include light emitting diodes, electro-luminescent light sources, and chemoluminescent (also called phosphorescent) sources. The present invention is particularly applicable to transportation headlamps for automobiles and bicycles, as well as to flashlights or any other lighting product that would conventionally utilize a metallic reflector. The present invention seeks to eliminate the need for a metallic or other reflector, and instead use only total internal reflection (TIR) and refraction.
A relevant prior art approach is disclosed by Janis Spigulis, "Compact dielectric reflective elements. I. Half-sphere concentrators of radially emitted light," Applied Optics, 33(35), Sep. 1, 1994, pages 5970 to 5974. This paper, however, is only concerned with forming a beam from the upward-going light, while the downward-going light requires a metallic reflector. For dealing with downward-going light, reflectors have several disadvantages: (1) reduced optical efficiency; (2) problems with integrating the reflected light with upward-going light; (3) increased cost and mechanical complexity. Accordingly, the present invention seeks to dispense with metallic or other type reflectors by using a second -outer transparent optical element to redirect the downward-going and sideways-going light into an annular beam, one that surrounds the beam formed from the upward-going light.
Automobile headlights typically have a light collecting efficiency of only twenty to thirty-five percent from the lamp to the beam. The present invention arms to eliminate or at least reduce the need for metallic reflectors in order to increase the light utilization efficiency from the filament to the beam to the range of seventy-five to ninety percent. Increased light utilization efficiency translates into a better level of road illumination or reduced electrical power consumption.